Seminarium Teorii Oddziaływań Elementarnych

The description of the decay law and its link to the energy distribution is shown in quantum mechanics (QM). Deviations from the exponential decay law exist at short and long times; experiments are discussed, in which these deviations have been seen. A related effect is the so-called Quantum Zeno effect, which forbids the decay (or a transition) of a quantum state that is observed at sufficiently small time intervals. Then, the attention is focused on the decay in the context of quantum field theory (QFT): it is shown that deviations from the exponential law occur also here. Similarities and differences with QM are discussed. The important case of the decay, in which more than one decay channel is present, is shown.